When using an end mill or other rotary tool to cut a workpiece surface, the workpiece surface is cut intermittently by the cutting blade. For this reason, the machined workpiece surface generally has a plurality of remaining convex uncut parts called “cusps”. Between the cusps, arc shaped dimples are formed. As a machining method which considers the shape error of the workpiece surface due to such cusps, for example, the machining method which is described in the following Patent Literature 1 is known.
In the machining method which is described in Patent Literature 1, while a rotary tool is made to move along the machining points while machining the workpiece surface, the rotary tool is made to rotate by one blade's worth of rotational angle between the machining points. On the other hand, a machining method which divides a machining surface by polygonal shaped patches and machines the insides of the patches along spiral shaped tool paths to form regular surface patterns at the machined surface is also known (for example, see Patent Literature 2).
However, neither of the methods which are described in the above Patent Literatures 1 and 2 considers how the arc shaped dimples which are formed at the machined workpiece surface are arranged at the workpiece surfaces as a whole. Therefore, for example, when machining a first machining area of the workpiece surface, then machining a second machining area which adjoins this first machining area, the dimples are formed regardless of the dimples of the first machining area. As a result, incompletely shaped dimples are liable to be formed at the boundary part of the first machining area and second machining area and these incompletely shaped dimples are liable to cause streak patterns and other undesired machining marks to remain at the workpiece surface.